This application relates to communications systems, particularly video systems. The application relates in particular to interconnection apparatus and methods for handling all of the electrical requirements for video systems, such as Closed Circuit TV (“CCTV”) systems, including those of the types used in video security systems.
In the past, buildings would have several cabling systems, respectively for different types of communications systems. For example, telephone wiring was used for voice, coaxial cable for data networks, multipair cabling for RS232/RS422 control data, etc. With all of the separate costs involved, this became a very inefficient and costly way to install these systems. A solution was to install a standard cable and connector system throughout a building which could, with some additional equipment, be used to support all or most of the different types of communication systems in use in the building. This standard cable and connector system is called a “Structured Cabling System” (“SCS”).
The SCS is a set of cabling and connectivity products that integrates voice, data, video and various building management systems (“BMS”), such as safety alarms, security access, energy systems, etc. Characteristics of an SCS include an open architecture, standardized media and layout, standard connection interfaces, adherence to national and international standards, and total system design and installation. Typically, SCS cable is a multipair cable made up of unshielded twisted pairs (“UTP”) of insulated copper conductors. A typical SCS cable includes four such twisted pairs. A typical building has a plurality of SCS cables, perhaps dozens or even hundreds, extending throughout the building. Apart from the SCS, the voice, data, video and BMS have nothing in common, except for similar transmission characteristics (analog or digital data signals) and delivery methods (conduit, cable, tray, raceway, etc.) that support and protect the cabling.
Although it has existed in the SCS in various configurations, CCTV has not been integrated as a complete system into the SCS, since systems equipment has not existed that would provide the means to conveniently interface all of the various types of CCTV cameras, Pan/Tilt/Zoom (“PTZ”) systems, monitoring equipment and switching equipment into the SCS. A CCTV system typically has three different types of electrical requirements, viz., control signals which must be sent to each camera and/or PTZ device to control its operation, video data which is sent from each camera to a receiver, and AC power for powering the camera and associated equipment, such as a PTZ unit. The control signals, which are typically in accordance with the RS422 standard, but could also be RS232 or RS485 (bidirectional), have historically been handled over a cabling system distinct from the SCS, and have not been transmitted over UTP cables.
Sending video over UTP cable has been done using the unbalanced-to-balanced line technique (video baluns) for 20 years or more. Baluns are typically passive devices that match impedance and provide common mode rejection. Northern International Technology (“NITEK”) has improved on this basic technology by introducing unique, adjustable, active receivers that provide improved common mode rejection and longer distances for transmission of video while maintaining signal integrity and video quality. Previously, transmitting video signals over one twisted pair of SCS cable required the user to provide his own connector and interface equipment. NITEK provides an integrated system for transmitting video signals over one pair of an SCS cable, but the AC power and control signals must still be separately provided. In the security industry, UTP for transmission of video has become increasingly popular over the past five years, as more dealers have been willing to use it in CCTV installations. Problems with earlier systems using technology that was prone to drifting and, in some cases, susceptible to voltage surges, made dealers wary of the technology. Greater acceptance of this technique has come about recently due to lower cost balun devices and the convenience and size advantages of using UTP cable, as opposed to coax cable, for multiple cameras. This has resulted in larger camera projects (hundreds of cameras) using UTP. In response to these larger system requirements, NITEK introduced rack mounted systems that could accept as many as 40 inputs per rack. Such systems are currently primarily targeted for sale through the security system installer/dealer. The systems are typically stand-alone CCTV systems, either connected to existing communication cables or using new UTP cables (mostly CAT 5) installed specifically for the CCTV System.
Some CCTV cameras are provided with local power, i.e., a power supply adapted to be plugged into the 120-volt AC system at the camera location. But many multi-camera video systems power the cameras from a central fused power supply, power from which has, heretofore, been provided independently of the SCS.